The balsam woolly adelgid (Adelges piceae) is small wingless insect that infests and kills firs.

The Great Smoky Mountains National Park, straddling North Carolina and Tennessee in the Southeastern United States, contains about 75% of all southern spruce-fir ecosystems.

These ecosystems covered vast portions of the Southeast during the Last Glacial Period, when the climate was cool and moist.

Although some areas are being regenerated by young firs, there is much change in understory composition, including invasion by both woody and herbaceous species.

[1] Although the fir population in the Great Smoky Mountains National Park was decimated by woolly adelgids in the 1960s through 1980s, there has been some recovery since then.